Southern Ontario wetlands provide $4.2 billion in sediment filtration and phosphorus removal services each year, keeping our drinking water sources clean and helping to mitigate harmful algal blooms and pests in our lakes and rivers.
A new study from the University of Waterloo uses economic valuation to help us understand the importance of southern Ontario wetlands for water filtration – especially as these sensitive ecosystems continue to be lost through conversion to agriculture or urban development.
“Wetlands naturally filter phosphorus and sediment from water, but their value is often largely overlooked,” said Tariq Aziz, who conducted the study during his PhD and postdoctoral work at the Department of Earth Sciences. and environment of Waterloo. “By calculating the economic value of wetland filtration and comparing it to the costs of engineering interventions, we hope to reinforce the importance of protecting our wetlands.”
The total value of $4.2 billion in sediment and phosphorus filtration services was determined based on the average rate of sediment accumulation in each type of wetland in southern Ontario and by estimating how much the removal and disposal of the same amounts of sediment and phosphorus at stormwater management facilities in Ontario would cost.
This is the first economic valuation study to separate the values of the major wetland types in southern Ontario: marshes, bogs, swamps and fens. “We found marshes to be the most valuable wetland type for sediment and phosphorus filtration, based on removal rates per hectare,” Aziz said. “However, because swamps make up 87% of southern Ontario’s wetlands, they contribute about 80% of all filtration services we receive, worth about $3.4 billion per year.
This study also calculated how much it would cost to replace the wetlands’ existing phosphorus filtration function with three different man-made solutions. Constructing artificial wetlands would cost an average of $2.9 billion per year to replace the free phosphorus filtration service that our natural wetlands currently provide. Implementing agricultural best management practices to remove an equivalent phosphorus load would cost society $13 billion a year, while expanding current wastewater treatment capacity to replace area filtration service wetlands would cost $164 billion a year.
The study “Economic Valuation of Suspended Sediment and Phosphorus Filtration Services by Four Different Wetland Types: A Preliminary Assessment for Southern Ontario, Canada”, authored by Aziz and his supervisor, Professor Philippe Van Cappellen, was published in the journal Hydrological Processes.